GEOLOGY, SCARP MORPHOLOGY AND FAULT KINEMATICS OF THE NORTHERN VOLCANIC TABLELAND, OWENS VALLEY, CALIFORNIA

Only a few studies exist of the northern area of Owens Valley´s Volcanic Tableland, a low plateau covered by massive 764 ka old pyroclastic flow deposit (Bishop tuff). In this seismically active region the tuff displays a unique network of nicely preserved scarps as surface expression of normal faulting. The purpose of our work is to improve the existing data (geology and scarp morphology) in order to better understand fault kinematics in northern Owens Valley. To accomplish this, we carried out detailed geological and geomorphological mapping of the area from both high-resolution satellite images and fieldwork.

We found that the geology is more complex than previously thought. In addition to unmapped graben structures, we identified many N-S striking scarps as high as 40 m. Theses scarps are commonly situated in the partly-welded tuff and reflect multiple rupture events. We recognized two main types of scarps based on their morphology: 1) short, high and bow-shaped, and 2) long, low and straight. Each type reflects a different tectonic history.

Although the major faults in the northern Owens Valley show right-lateral motion, previous studies have not reported strike-slip offset from the Volcanic Tableland. We have however found drainages and small structures in the tuff that show NNW-trending right-lateral offsets, which are possibly related to displacement along the Chalfant Valley fault. The latter is well-imaged by seismicity along the southeastern edge of the Tableland, but its continuation further north is unclear.